Epoxy resin compositions



United States l atent Ofitice 3,227,679 Patented Jan. 4, 1966 3,227,679EPOXY RESIN COMPOSITIONS Gordon P. Brown, Schenectady, N.Y., assignor toGeneral Electric Company, a corporation of New York No Drawing. FiledJune 24, 1960, Ser. No. 38,426 9 Claims. (Cl. 260-47) This inventionrelates to epoxy resin compositions. Moreparticularly, it relates to newand useful epoxy resin compositions which are cross-linked by means ofisocyanate-aryl alkyl amine adducts, said compositions beingcharacterized by desirably long shelf life and being useful for manyapplications including adhesives, coatings, castings and moldingmaterials.

The use of amines to cure epoxy resins is well known, as is the use ofisocyanate materials for the same purpose of cross-linking. It Will beappreciated, of course, that the use of isocyanate materials presents ahealth hazard due to the .toxicity of the isocyanate. It is, therefore,the general practice to block or temporarily inactivate the isocyanategroups by reacting them as with a material containing reactive hydrogen,which ties up, masks or blocks some or all ofthe isocyanate groups atordinary temperatures, but which will split off at elevatedtemperatures, regenerating the isocyanate groups so that they may reactwith the hydroxyl or other reactive group of the epoxy resin, producinga three-dimensional polymer. Among the so-called blocking materialswhich have been used to temporarily mask the isocyanates are compoundsof the phenol type. However, phenol is somewhat toxic in and of itself.Furthermore, if the isocyanate is to be used in curing an epoxy resin,it follows that the phenol must be removed or evolved as byvolatilization, since it would dilute the epoxy resin composition. Suchvolatilization may lead to bubbling or foaming, and even in essentiallycomplete volatilization or removal of the phenol, leave detrimentalsmall molecular weight fractions in the final epoxy resin composition.From the above, it will be quite apparent that there is a definite needfor an isocyanate adduct material which can be used to cure epoxyresins,

but which at the same time is blocked or masked to curb its toxicityand, furthermore, in which isocyanate groups are blocked with a materialwhich itself is a curing agent for the epoxy resin, so that there is noneed for removal of a component of theadduct after it has beendecomposed or. split apart.

A principal object, therefore, of the present invention is to provideepoxy resin compositions which are cured by an isocyanate adduct, theentire adduct entering into 'reaction with the epoxy resin to provide atightly crosslinked three-dimensional polymeric material.

1 Briefly stated, the present invention relates to epoxy resincompositions which are cured with an adduct or reaction product of apolyisocyanate and an aryl alkyl amine.

Those features of the invention which are believed to be novel are setforth in the claims appended hereto. The invention however, be betterunderstood and further objects and advantages appreciated from aconsideration of the following description:

The isocyanate materials used in connection with the present inventionare polyisocyanates, or those having more than one isocyanate group permolecule. Examples of such polyisocyanates are alkylene diisocyanates,such as ethylene diisocyanate, trimethylene diisocyanate, hexamethylenediisocyanate, propylene-1,2-diisocyanate, and

ethylidine-diisocyanate; cyclo-alkylene diisocyanates, such ascyclopentylene diisocyanate; aromatic diisocyanates, such. as tolylene.diisocyanate; naphthylene diisocyanate,

1,4-phenylene diisocyanate. Other well known polyisocyanates of theabove types as well as alkyl aryl diisocyanates among others are useful.Among the triisocyanates which are useful are triphenylmethanetriisocyanate, benzene triisocyanate, tolylene triisocyanate, silicontriisocyanate, ethylenetetraisocyanate, and diphenyl triisocyanate. Ingeneral, any polyisocyanate or one containing more than one isocyanategroup per molecule can advantageously be used herewith.

Polyisocyanates having a greater number of isocyanate groups permolecule than 2 may be prepared by reacting typical diisocyanates suchas those above with-polyhydric compounds, such as glycerine, trimethylolpropane, pentaerythritol, the amounts of polyhydric material being usedin equivalent amounts to the diisocyanate.

The blocking agent used in connection with the present inventionconsists of aryl alkyl amines, including mixtures of such amines. It hasbeen found that only these materials fulfill the requirements of theinvention for a reactive material but one which at the same time willnot react too readily. For example, it has been found that adducts ofpolyisocyanates and alkyl amines will not properly split when heated toelevated temperatures. On the other hand, adducts of aryl amines andpolyisocyanates have a short shelf life, measured in days and weeks,i.e., the reaction between such adducts and the epoxy resin will takeplace at room temperature over relatively short periods of time. On theother hand, it has been unexpectedly found that aryl-alkyl aminesrequire a temperature of about C. for decomposition and reaction withthe epoxy resin, and that compositions of such materials with epoxyresins have a shelf life of up to over 5 years or of about 5 years ormore. In effect, the polyisocyanate-aryl alkyl amines of the presentinvention provide a curing agent for the epoxy resin which will notsplit or be reactive either insofar as the isocyanate group or the aminegroups are concerned, until the proper reacting conditions of elevatedtemperature are met.

Any of the usual aryl alkyl amines are useful in this applicationincluding but not limited to Nalkyl anilines, such as N-methyl, N-ethyl,N-mpropyl, N-cyclohexyl aniline etc.; N-alkylhalo anilines, such asN-methyl-ochloroaniline, N methyl-p-chloroaniline etc.; N-alkyltoluidines; N-alkyl naphthylamines; N-phenyl benz ylamines; and vN,N'-diphenyl alkylene diamines, such as N,N'-diphenyl-1,2 ethylenediamine. Others will occur to those skilled in the art,

The epoxy resins or ethoxyline resins which are useful in connectionwith the present invention are Well known and are profusely described inthe prior art, including the technical and patent literature. They aredisclosed for example in Castan Patent 2,324,483, as well as CastanPatent 2,444,333, British Patent 518,057 and British Patent 579,698.Essentially these ethoxyline resins are based on the resinous product ofreaction between an epihalohydrin, for instance, epichlorohydrin and aphenol having at least two phenolic hydroxy groups, for example, bis-(4-hydroxyphenyl) dirnethyl propane. Further examples of ethoxylineresins which may be employed in the practice of the present inventionare disclosed in US. Patents 2,494,295, 2,500,600 and 2,511,913. Byreference, the aforementioned patents are intended to be part of thepresent description of the ethoxyline resins usedand, for brevity, thenethoxyline resins will not be described other than that they containmore than one ethylene oxide group, e.g., from one to two or moreepoxide groups per molecule and may be prepared by effecting reactionbetween a polyhydric phenol or alcohol, for example, phenol,hydroquinone, resorcinol, glycerine and condensation 4- EXAMPLE 1 Atriisocyanate was prepared by adding 1044 parts by weights of tolylenediisocyanate dropwise with stirring to 628 parts of trimethylol propanein 648 parts by weight of products of phenols with ketones, for instancebis-(4-hydroxylphenyl)-2,2-propane, with epicholorohydrin. For example,the reaction of epichlorohydrin with bis-(4-hydroxylphenyl)-2,2-prpanemay be formulated as follows:

Alkali noOoQ-on ClCH2-CHCH2 where n has an average value varying fromaround zero ethyl acetate. The reaction was carried out in a flask toabout 9. Many of these ethoxyline resins are sold fitted with refluxcondenser, stirrer, dropping funnel, and under the name of Epon resinsby Shell Chemical Cornitrogen inlet tube. Dry nitrogen gas was passedthrough poration, or Araldite resins by the Ciba Company. Data thereaction mixture during the course of the reaction and on several of theEpon resins found suitable for the inafter the addition of the tolylenediisocyanate, was comstant purpose are given in the table below: plete,the mixture was refluxed for 15 minutes, to obtain the triisocyanatematerial.

Table 1 EXAMPLE 2 The triisocyanate of Example 1 was blocked with ethylEPOXY Resin ggf 5 6- aniline as follows. There was added to 436 parts of66% triisocyanate solution 161 parts of ethyl aniline dissolved 9 in53.8 parts of ethyl acetate, the addition being made $811333 i i Lulu;dropwise in apparatus similar to that of Example 1, the 333 additionbeing made over the course of one hour, during E m oa i aoears 4H5 whichtime the reaction was kept at reflux temperature by 3331;: ggg g? Egfigthe heat of reaction; the resultant material was a triisocya- ERL 2774175-200 Liquid nate blocked with an aryl alkyl amine, in this instanceethyl $5533 3774 5382 anilinea The following examples illustrate thepreparation of epoxy resin compositions incorporating aryl alkyl amineThe complex epoxides used contain epoxide groups or s i ii ggggcomposltlons of the types epoxide and hydroxyl groups as theirfunctional groups EXAMPLE 3 and are generally free from other functionalgroups such as basic and acidic groups 1.2 grams (0.01 equivalent) ofethyl aniline was mixed Also included in the present invention are epoxyresins 4 with 2.2 grams (0.01 equivalent) of the tolylene diisocyderivedfrom polyfunctional phenols of the novolac type. mute-trimethylol P preaction Product Of mpl 1 h epoxidized novolac resins are d d b h insolution in 1.1 grams of ethyl acetate and allowed to Borden ChemicalCompany under tho trade name Epiphen stand about 10 minutes until theinitial heat Of reaction and by the Dow Chemical Company Ggnerally, uchhad dissipated and the SOlIltlOlJ W35 nearly gelled. There resins aremade by epoxidizing novolac resins which in Were added to this Solutiongrams eq of turn are made in the usual well-known way. Among the P ntogether with grains of ethyl acetate for patents relating to epoxidizednovolac resins is Patent Solution P P The solvent was evaporated 01f and2,658,885, such patents being familiar to those skilled in the CureCarried out y heating to about for V the art. Among the specific usefulepoxylated novolac houf- The resulting Piustic WuS hard, inflfixibie,iniusibie, resins is Dow D.E.N.438, which has a molecular weight andcross-linkedof 600, a functionality of 3.3, an epoxy equivalent weightEXAMPLE 4 of 175 to 182, a specific gravity of 1.220, a viscosity atThere were added to 1.1 grams (0'01 6 uivalent 125 F. of about 30,000 to90,000 cps. Epiphen, a p diphenyl ethylene diamine, 2.2 grams of tliereactioii pi'oductfii the P chemical Company: has an epoxy not oftolylene diisocyanate and trimethylol propane (Exequivalent weight offrom about 180 to 200, and a funcample 1) in L1 grams of ethyl acetate.When the heat of f i of a Specific giavity of about The reaction haddissipated, there were added to the solution VISCOSiZY of this resin at75 F. 15 about 750,000 cps., and 2.0 grams of Epon 828 and the mixturewas cured for at 1 10 F. is about 60, 00 cps. p p an P Y about 10 to 15minutes at 200 C., resulting in an infusible equivalent weight of 180 to200, a functionality of 3.3, crossfinked materiaL a specific gravity of1.12, and a viscosity at 25 F. of from about 75,000 to 150,000 cps.Another epoxylated novolac EMMPLE 5 i DOW X having a functionality of aExample 2 was repeated except that instead of an equivvlscoslty at Oi425,000 1 and an P Y eq lvalent ratio of ethyl aniline to triisocyanateof 1:1, this al t W ight of a t ratio was changed to 2:3. Thus, theisocyanate of this exi useful among etnnifyiene l'eslns are the P 3ample had one free and two blocked isocyanate groups per s y e r f 2 -tY y phenyuethane, molecule, as contrasted with that of Example 2, inwhich such resin being known as Epon 1310 and manufactured ll f hisocyanate groups are 1 by the Shell Chemical Company. Other usefulmaterials are the epoxidized polyenes. EXAMPLE 6 Preferably, the adductand epoxy resin are used in about A molding composition was made bymixing 5.2 grams stoichiometric amounts in order to achieve the bestphysical characteristics.

The following examples illustrates the preparation of the polyisocyanatematerials and their blocking with aryl alkyl amines.

of Epon 834 on a hot plate with mixing, with 6.0 grams of thepolyisocyanate adduct of Example 5. The material of stoichiometricproportions Was thoroughly mixed, cooled, solidified, and ground. Fivegrams of the powder so obtained were cured for /2 hour at 180 C. under20,-

5.2 grams of Epon 834 were mixed on a hot plate as in the precedingexample, with 3.0 grams of the polyisocyanate adduct of Example 5. Whencooled, ground and pressed as in the previous example, theelectricalproperties of the material were found to be as in Table IIIbelow:

Table III Temperature PF Dielectric Constant The higher power factor isattributable to the fact that the adduct-epoxy composition was notstoichiometric as in Example 6.

EXAMPLE 8 A coating composition was made by shaking for about 3 hours24.2 grams ethyl aniline, 50.6 grams ethyl acetate, 50.6 grams butylacetate, 50.6 grams Cellosolve acetate, 50.6 grams toluene, 43.8 gramsof the triisocyanate of Example 1, 97.4 grams Epon 1001, 0.8 gramcellulose acetate butyrate, and 8 grams of polyvinyl butyral resin. Theresulting solution had an efliux time from Zahn cup #2 of 26.3 seconds,and after one weeks aging the efilux time had increased only to about31.2 seconds. This composition when coated on steel panels had favorablecharacteristics including good abrasion resistance and scratch hardness.

EXAMPLE 9 A casting sample was made by mixing 5.2 grams Epon 834 and 6.8grams solvent-free blocked polyisocyanate adduct prepared as in Example2. The constituents were mixed on a hot plate and cured for two hours at150 C. and /2 hours at 180 C. The electrical properties of this materialare as shown in Table IV below.

Table IV Power Resistivity, Dielectric Temperature, 0. Factor, ohm cm.Strength, Volts/ Percent Mil 25 0. 40 7. 4X10 520 (43 mil thick 100. 3.O sample). 150 17. 3. X10

three-dimensional epoxy resin compositions. The present inventionprovides materials which as compared to the usual amine-epoxy resincompositions are characterized by an extendedshelf life. At the sametime, since both components of the ad-du-ct serve as curing agents,there is no need as in the usual blocked polyisocyanate 'materials tovolatilize or remove the masking agent from the adduct before it can beusefully employed as a curing agent.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. AIheat-curable epoxy resin composition comprising one equivalent ofan epoxy resin containing more than 1, 2-epoxide group and from 0.5 to 1equivalent ofthe reaction product of (l) polyisocyanate and (2) an amineselected from the group consisting of N-alkyl anilines, N-cyclo hexylanilines, N-alkylhalo anilines, N-alkyl toluidines, N-alkylnaphthylamines, N-phenyl benzylamines, N,N'-diphenyl alkylene diaminesand mixtures thereof, the proportions of (l) and (2) beingsuch that saidreaction product is a material selected from the group consisting of (a)a reaction product in which all isocyanate groups are reacted with saidamine, (b) a reaction product in which all but one of said isocyanategroups are reacted with said amine, and (c) mixtures of (a) and (b).

2. A coating composition comprising the epoxy resin composition of claim1.

3. Molding and casting compositions comprising the epoxy resincomposition of claim 1.

4. The heat-reacted composition of claim 1.

5. A heat-curable epoxy resin composition comprising one equivalent ofan epoxy resin containing more than one 1,2-epoxide group and from 0.5to 1 equivalent of the reaction product of (1) polyisocyanate and (2) anamine selected from the group consisting of N-alkyl anilines,N-cyclohexyl anilines, 'N-alkylhalo anilines, N- alkyl toluidines,N-alkyl naphthylamines, N-phenyl benzylamines, N,N-diphenyl alkylenediamines and mixtures thereof, the proportions of (l) and (2) being suchthat said reaction product is a material selected from the groupconsisting of (a) a reaction product in which all isocyanate groups arereacted with said amine, (b) a reaction product in which all but one ofsaid isocyanate groups are reacted with said amine, and (1:) mixtures of(a) and (b), the polyisocyanate being the reaction product of tolylenediisocyanate and a monomeric polyhydric alcohol.

6. A heat-curable epoxy resin composition comprising one equivalent ofan epoxy resin containing more than one 1,2-epoxide group and from 0.5to 1 equivalent of the reaction product of (l) polyisocyanate and (2)ethyl aniline, the proportions of (l) and (2) being such that saidreaction product is a material selected from the group consisting of (a)a reaction product in which all isocyanate groups are reacted with saidamine, (b) a reaction product in which all but one of said isocyanategroups are reacted with said amine, and (c) mixtures of (a) and (b).

7. The process of curing an epoxy resin composition which comprisesadding to one equivalent of an epoxy resin containing more than one1,2-epoxide group from 0.5 to 1 equivalent of the reaction product of(1) a polyisocyanate and (2) an amine selected from the group consistingof N-alkyl anilines, N-cyclohexyl anilines, N- alkylhalo anilines,N-alkyl toluidines, N-alkyl naphthylamines, N-phenyl benzylamines,N,N-diphenyl alkylene diamines and mixtures thereof, the proportions of(l) and (2) being such that said reaction product is a material selectedfrom the group consisting of (a) a reaction product in which allisocyanate groups are reacted with said amine, (b) a reaction product inwhich all but one of said isocyanate groups are reacted with said amine,and (0) mixtures of (a) and (b), and heating to the order of at least C.to decompose said reaction product and cure said epoxy resin.

8. A heat-curable epoxy resin composition comprising one equivalent ofan epoxy resin containing more than vone 1,2-epoxy group and 0.5 to 1equivalent of the reaction product of (1) polyisocyanateand (2) an amineselected from the group consisting of N-alkyl anilines, N-cyclohexylanilines, N-alkylhalo anilines, N-alkyl toluidines, N-alkylnaphthylamines, N-phenyl benzylamines, N,N'-diphenyl alkylene diaminesand mixtures thereof, the proportions of (1) and (2) being such thatsaid reaction product is one in which all isocyanate groups are reactedwith said amine.

9. A heat-curable epoxy resin composition comprising one equivalent ofan epoxy resin containing more than one 1,2-epoxide group and from 0.5to 1 equivalent of the reaction product of 1) polyisocyanate and (2) anamine selected from the group consisting of N-alkyl anilines,N-cyclohexyl anilines, N-alkylhalo anilines, N- alkyl toluidines,N-alkyl naphthylamincs, N-phenyl benzylamines, N,N-diphenyl alkylenediamines and mixtures thereof, the proportions of (1) and (2) being suchthat in the reaction product all but one of said isocyanate groups arereacted with said amine.

References Cited by the Examiner UNITED STATES PATENTS OTHER REFERENCESLee et a1.: Epoxy Resins, McGraw-Hill Book Co. 1957, pages 69, 159Qand160.

Winkler: German Pat. No. 1,055,808, April 23, 1959,

abstract in Chem. Abstracts, vol. 55, No. 4, page 4047d,

February 20, 1961.

'WILLIAM H. SHORT, Primary Examiner.

20 PHILIP MANGAN, HAROLD N. BURSTEIN,

' Examiners.

1. A HEAT-CURABLE EPOXY RESIN COMPOSITION COMPRISING ONE EQUIVALENT OFAN EPOXY RESIN CONTAINING MORE THAN 1, 2-EPOXIDE GROUP AND FROM 0.5 TO 1EQUIVALENT OF THE REACTION PRODUCT OF (1) POLYISOCYANATE AND (2) ANAMINE SELECTED FROM THE GROUP CONSISTING OF N-ALKYL ANILINES,N-CYCLOHEXYL ANILINES, N-ALKYLHALO ANILINES, N-ALKYL TOLUIDINES, N-ALKYLNAPHTHYLAMINES, N-PHENYL BENZYLAMINES, N,N''-DIPHENYL ALKYLENE DIAMINESAND MIXTURES THEREOF, THE PROPORTIONS OF (1) AND (2) BEING SUCH THATSAID REACTION PRODUCT IS A MATERIAL SELECTED FROM THE GROUP CONSISTINGOF (A) A REACTION PRODUCT IN WHICH ALL ISOCYANATE GROUPS ARE REACTEDWITH SAID AMINE, (B) A REACTION PRODUCT IN WHICH ALL BUT ONE OF SAIDISOCYANATE GROUPS ARE REACTED WITH SAID AMINE, AND (C) MIXTURES OF (A)AND (B).